We intend to study the effect of administered iron and heme on the distribution of these compounds in the subcellular compartments of the isolated rat liver perfusion system. Special emphasis will be placed on investigation of the relationship between ferritin and hemopexin in aberrations of iron and porphyrin metabolism. We also plan to measure uroporphyrin synthetase activity for the diagnosis of acute intermittent porphyria and for assessing the effects of treatment. BIBLIOGRAPHIC REFERENCES: Effect of hemoglobin and hematin on plasma clearance of hemopexin, photoinactivated hemopexin and albumin. H.H. Liem, J.I. Spector, T.P. Conway, W.T. Morgan, and U. Muller-Eberhard, Proc. Soc. Exp. Biol. Med. 148:519-522, 1975. Porphyrin binding proteins in serum. U. Muller-Eberhard and W.T. Morgan, Ann. N.Y. Acad. Sci. 244:624-650, 1975.